Disclosed herein are systems and methods that relate to tools used for cutting bone during joint replacement surgery. One particular application is for a rib assembly to be used for cutting the cavity of the acetabulum when replacing the hip joint by a prosthetic cup. Other examples are patella resurfacing ribs, ribs used to plane the calcar when implanting a femoral component of a total hip replacement, and axial tapered or cylindrical long ribs used in hip or knee replacement used to find and shape the femoral canal and glenoid reamers that are used in shoulder arthroplasty.